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Re: Phytoplankton Changed Color 250 mya



Ah yeah. Easy to overlook in the Nature table of contents because the
paper's title is just "The evolutionary inheritance of elemental
stoichiometry in marine phytoplankton". Abstract (refs deleted):

Phytoplankton is a nineteenth century ecological construct for a
biologically diverse group of pelagic photoautotrophs that share common
metabolic functions but not evolutionary histories. In contrast to
terrestrial plants, a major schism occurred in the evolution of the
eukaryotic phytoplankton that gave rise to two major plastid superfamilies.
The green superfamily appropriated chlorophyll _b_, whereas the red
superfamily uses chlorophyll _c_ as an accessory photosynthetic pigment.
Fossil evidence suggests that the green superfamily dominated Palaeozoic
oceans. However, after the end-Permian extinction, members of the red
superfamily rose to ecological prominence. The processes responsible for
this shift are obscure. Here we present an analysis of major nutrients and
trace elements in 15 species of marine phytoplankton from the two
superfamilies. Our results indicate that there are systematic phylogenetic
differences in the two plastid types where macronutrient
(carbon:nitrogen:phosphorus) stoichiometries primarily reflect ancestral
pre-symbiotic host cell phenotypes, but trace element composition reflects
differences in the acquired plastids. The compositional differences between
the two plastid superfamilies suggest that changes in ocean redox state
strongly influenced the evolution and selection of eukaryotic phytoplankton
since the Proterozoic era.

And here from the rest of the paper...

The high requirements for Fe and Mn and low requirement for Mo in all
photoautotrophs presumably reflects the high solubility of Fe and Mn and the
low solubility of Mo, Cu and other transition elements under the reducing
conditions of early Proterozoic oceans, when oxygenic photosynthesis first
appeared. This basic elemental composition helped to underpin the ecological
success of the green superfamily throughout the late Proterozoic and the
Palaeozoic eras. After the end-Permian extinction, and ocean anoxoic [sic!]
events in the Triassic and Early Jurassic periods, the red superfamily rose
to ecological prominence. The relatively low Fe and Mn quotas and high Cd,
Co and Mo quotas in the red superfamily suggests an adaptation of the
photosynthetic apparatus and ancillary supporting proteins to a highly
oxidized surface ocean, presumably in the latter half of the Phanerozoic
eon.

Fe = iron
Mn = manganese
Mo = molybdenum
Cu = copper
Cd = cadmium
Co = cobalt

Sounds like they imply that the ocean burnt down in the P-Tr mass
extinction. Interesting...